CODEWITHSUNDEEP
c++
CLearner
CLearner

Reputation: 542

C++ Zero-out a struct array?

struct OBJECT
{
unsigned int Var1;
std::string Str1;
...
bool YesNo;
};

OBJECT Obj[ 327 ];

I am confused about how to zero-out Obj. It has several different type of elements. Do I have to set all of its member to 0? Like... Obj[0].Str = ""; ? So the question is, what is the proper way of doing it?

My attempt:

::memset( &Obj, 0, sizeof( Obj ) );

I am not sure if I am doing it correctly...

Oh and are there any faster way to zero-out an array?

Upvotes: 1

Views: 2240

Answers (4)

Alex Chamberlain
Alex Chamberlain

Reputation: 4207

You should change your declaration to

struct OBJECT
{
    unsigned int Var1;
    std::string Str1;
    ...
    bool YesNo;

   OBJECT()
   : Var1()
   , Str1()
   , ...
   , YesNo(false)
   {
       // Do Nothing
   }
};

The array - which you should use over std::array or std::vector - will initialise the objects.

Upvotes: 1

Olaf Dietsche
Olaf Dietsche

Reputation: 74018

Don't do it this way, because you have non trivial members in your struct (e.g. std::string). You can do this if all your members are only simple data types, like int, char, double or pointers.

The correct way for this type of struct is to define a constructor, which initializes all members properly 

struct OBJECT {
    OBJECT() : Var1(0), YesNo(false), ... {}

    unsigned int Var1;
    std::string Str1;
    ...
    bool YesNo;
};

Upvotes: 10

Zeta
Zeta

Reputation: 105876

Either provide a custom default constructor or use the compiler defined default constructor:

std::fill(std::begin(Obj), std::end(Obj), OBJECT());

Note that the fill approach fill only work if you use the default constructor.

Upvotes: 3

Jonathan Potter
Jonathan Potter

Reputation: 37122

The "correct" way is to add a constructor method for your struct that initialises any member variables that don't have constructors of their own, e.g.:

OBJECT_STRUCT()
: Var1(0)
, YesNo(false)
{
}

In that example you'll note that Str1 was not initialised; this is because std::string has its own constructor that initialises it.

Upvotes: 3

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